MEMS combine miniaturized mechanical and electrical devices to make correspondingly small machines. MEMS fabrication builds upon and exploits the massive development that has taken place in semiconductor manufacturing processes with regard to integrated circuit technology. Thus, despite the difficulties presented by forming such miniature machines with precision tolerances, MEMS devices can be manufactured relatively economically on a mass scale.
A growing application of MEMS technology is in miniature cameras for applications such as cell phones. Initially, cell phone cameras were typically fairly crude affairs such a fixed focus plastic lens assembly. Better optical fidelity was unnecessary since the resolution of the associated image sensor was relatively poor. However, it now commonplace for cell phone cameras to have high-resolution (multiple-megapixel) imaging sensors. To exploit the image fidelity achievable with such pixel resolution, MEMS camera modules that provide autofocus modules and auto-shutter capabilities have been developed. High-fidelity optics require considerable precision with regard to alignment of lens and other elements in the light path that is readily achieved by MEMS developments such as disclosed in commonly-assigned U.S. Pat. No. 7,477,842, the contents of which are incorporated by reference.
MEMS devices such as camera modules are typically mounted onto some sort of substrate or base. But as discussed above, optical modules require considerable precision in their construction. This precision alignment may be adversely affected if strain from the MEMS mount couples into the MEMS device itself. For example, a common base substrate is plastic, which has a different thermal coefficient of expansion as compared to the semiconductor such as silicon used to form the MEMS device. Thermal changes can thus introduce strain between the MEMS device and its mounting substrate.
Another source of strain for MEMS devices stems from the electrical contact technique used to couple an electrical power source to the MEMS device. For example, a MEMS camera module may include an electrostatic actuator for actuating the focusing lens or other components that requires an electric power source. In that regard, it is conventional to use wire bonding or other techniques to couple to the MEMS electrical contacts. The wires can then mechanically stress the MEMS device.
Accordingly, there is a need in the art for MEMS devices with electrical contacts that isolate the MEMS devices from mechanical stress.